Hydrogen-absorbing materials are used in many applications, including processes involving the storage, recovery and supply of hydrogen. Industries such as hydrogen processing and energy conversion use such materials in hydrogen purification and separation processes.
Hydrogen energy sources are widely viewed and promoted as a clean, renewable energy source. Accordingly, improved and more efficient ways to produce, store, and transport hydrogen are needed.
Various metals and metal alloys can absorb and then desorb large amounts of hydrogen under appropriate temperature and pressure conditions. These materials are referred to as metal hydrides and are well known in the art. They include pure metals such as Mg, Pd, Ti, Pt, U, and alloys such as those based on nickel, lanthanum and aluminum.
Metal hydrides are used in many different forms. Although frequently used in the form of granules, metal hydrides are sometimes incorporated into a matrix such as a polymer. (See, for example, U.S. Pat. No. 4,110,425, issued to Buhl et al.)
Similarly, porous polymeric matrices are used as media for supporting metal hydrides and other hydrogen-absorbing materials because of the increased surface area and corresponding increase in the amount of hydrogen that can be absorbed in a given volume. Such compositions are disclosed in U.S. Pat. Nos. 4,433,063, issued to Bernstein et al, and 4,036,944, issued to Blytas.
U.S. Pat. No. 5,411,928, incorporated herein by reference, discloses a hydrogen-absorbing composition prepared by a sol-gel process. In that application, a sol is prepared from an organometallic compound, such as tetraethoxysilane, and mixed with hydride particles. The mixture is allowed to polymerize and then to cure to form a highly porous matrix having hydride particles dispersed throughout. The resulting composition has pores large enough to allow gases to pass through the matrix, yet small enough to hold the particles in place during repeated hydrogen absorption/desorption cycles without having significant breakdown and consequent release of the hydride particles into the process stream.
However, there remains a need within the art for a hydrogen separation and storage apparatus and process which is compatible with separating hydrogen from diverse gas streams such as refinery gas or industrial waste gas streams. Often these sources contain metal hydride poisons such as CO or H.sub.2 S which render the metal hydrides unusable. The prior art fails to provide a metal hydride separation technology capable of directly and selectively removing hydrogen from gas streams containing metal hydride poisons.